1.   Competent authorities shall calculate the net open interest in an agricultural commodity derivative or a critical or significant commodity derivative by aggregating the number of lots of that commodity derivative that are outstanding on trading venues and reported positions in economically equivalent OTC contracts over a representative period of time. Competent authorities shall calculate the net open interest in that commodity derivative based on position reporting data.

2.   By way of derogation from paragraph 1, when trading in a commodity derivative is transferred from one Union trading venue to another, or a third country trading venue to a Union trading venue, following a merger, business transfer or other corporate event or from one or more existing commodity derivatives to a commodity derivative newly admitted to trading on the same trading venue or in other similar circumstances, the competent authority shall calculate the open interest in that commodity derivative by taking into account the open interest on the former venue or in the former commodity derivatives. After a 6-month period, the competent authority shall calculate the open interest in accordance with paragraph 1.